India has formally commissioned a nuclear-powered submarine into its navy, rejoining the elite club of nations with such a weapon.
The $1bn Russian-built vessel is being leased by the Indian navy for the next 10 years.
It was handed over to India in eastern Russia in January.
India previously operated a Soviet nuclear submarine until 1991.
It now rejoins China, Russia, the US, the UK and France as an operator of nuclear submarines.
India is also developing its own nuclear-powered submarine which is expected to be ready by the end of this year.
Significantly, the submarine will be deployed on India's east, and not west, coast which means China -not Pakistan - is the clear threat.
In keeping with international non-proliferation treaties, the submarine will not be equipped with nuclear weapons.